1. Technical Field
The present disclosure relates to pedicle screws and, more particularly, to a pedicle screw having a proximal flange that is easily accessible to facilitate the connection of a gripping tool for locking and unlocking the pedicle screw.
2. Background of Related Art
The human spine is the supporting axis of the body and makes all the movement of a person's head, arms, and legs possible. It is a highly flexible structure, capable of a high degree of curvature and twist in nearly every direction. An adult spine generally has twenty-four vertebrae, which may be categorized into three major sections. These categories include the cervical spine, the thoracic spine, and the lumbar spine. The cervical spine is composed of the upper seven vertebrae, the thoracic spine is composed of the next twelve vertebrae, and the lumbar spine is composed of the final five vertebrae. Below the lumbar spine is a bone called the sacrum, which is part of the pelvis. Muscles and ligaments are attached to a slender projection from the back of the vertebrae known as the spinous process. Housed within a narrow channel in the center of spine is the spinal cord. All the nerves of the body are connected to the spinal cord.
Spinal pathologies, whether the result of genetic or developmental irregularities, trauma, chronic stress, tumors, or disease may limit the spine's range of motion or threaten critical elements of the nervous system housed within the spine. A variety of systems to correct the alignment of the spinal vertebrae involving the implantation of artificial assemblies in or on the spine have been devised.
For example, it is a common surgical requirement to stabilize and fix bones and bone fragments in a particular spatial relationship to correct the location of skeletal components due to injury or disease. This may be accomplished by using a number of bone pins, anchors, or screws placed in bones across a discontinuity in the bone or bone fragments, such as a fracture, or adjacent vertebrae, or a joint, connected by a rod to maintain a predetermined spatial location of the bones or bone fragments. In some cases, the use of these devices may be permanently implanted in the subject. In other cases, the devices may be implanted only as a temporary means of stabilizing or fixing the bones or bone fragments, with subsequent removal when no longer needed. It is also common that device implants that were intended to be permanent may require subsequent procedures or revisions as the dynamics of the subject's condition warrant. Additionally, spinal fixation apparatuses are widely employed in surgical processes for correcting spinal injuries and diseases. These apparatuses commonly employ longitudinal link rods secured to the bone such as vertebrae by spinal bone fixation fasteners such as pedicle screws, hooks and others.
Moreover, depending upon how such systems are coupled to the spine, the systems may be classified as anterior, posterior, or lateral implants. For example, lateral and anterior systems are coupled to the anterior portion of the spine. Posterior systems generally comprise a pair of rods that are fixed to adjacent vertebrae with pedicle screws or hooks on either side of the spinous process along a section of the spine. Achieving the optimum alignment of a system with the vertebrae to which it is to be coupled is limited by the range of motion achievable by the system, i.e., the greater the range of motion achievable by the assembly, the more closely aligned the assembly may be with the vertebrae. In addition to the limited range of motion achievable by current systems, currently available systems are often complex, unreliable, and difficult to manipulate.